I bought C-408 back in 1993 and used it during my military service to chat with some other operators when I was on very boring duty. It fit perfectly into the little pocket on the sleeve of my left upper arm. In order to talk, I just pressed the PTT through the cloth. It looked a little like Captain Picard pushing the PTT on his communicator which is part of his suit. My comrades were wondering in those days, but I replied, in 10 yearss' time, you all will have such a little device. Still, mobile phones are kind of big, but I envisage the time when communication devices will be woven into all our clothes. Then Captain Picard will no longer need to wear the same suit for all the year...
The C408 fits into your palm. And if you turn it around and slip the battery case open, you will notice that all the electronic components make up only about half the case. This made me understand that radio devices could be built still much, much smaller than as of thence in 1993. Today, most of the electronics of the C-408 would probably fit into a tenth of the space of the C-408 case. The only thing which consumes still as much space as back in 1993 are the batteries (2x AA).
Interesting pages on the C-408: